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powerpc/rtas: mandate RTAS syscall filtering

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CONFIG_PPC_RTAS_FILTER has been optional but default-enabled since its
introduction. It's been enabled in enterprise distro kernels for a
while without causing ABI breakage that wasn't easily fixed, and it
prevents harmful abuses of the rtas syscall.

Let's make it unconditional.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221118150751.469393-10-nathanl@linux.ibm.com
This commit is contained in:
Nathan Lynch
2022-11-18 09:07:47 -06:00
committed by Michael Ellerman
parent f975b6559b
commit 98c738c8ce
2 changed files with 0 additions and 29 deletions
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13
arch/powerpc/Kconfig
View File

@@ -1044,19 +1044,6 @@ config PPC_SECVAR_SYSFS
read/write operations on these variables. Say Y if you have
secure boot enabled and want to expose variables to userspace.
config PPC_RTAS_FILTER
bool "Enable filtering of RTAS syscalls"
default y
depends on PPC_RTAS
help
The RTAS syscall API has security issues that could be used to
compromise system integrity. This option enforces restrictions on the
RTAS calls and arguments passed by userspace programs to mitigate
these issues.
Say Y unless you know what you are doing and the filter is causing
problems for you.
endmenu
config ISA_DMA_API

16
arch/powerpc/kernel/rtas.c
View File

@@ -1050,8 +1050,6 @@ noinstr struct pseries_errorlog *get_pseries_errorlog(struct rtas_error_log *log
return NULL;
}
#ifdef CONFIG_PPC_RTAS_FILTER
/*
* The sys_rtas syscall, as originally designed, allows root to pass
* arbitrary physical addresses to RTAS calls. A number of RTAS calls
@@ -1200,20 +1198,6 @@ static void __init rtas_syscall_filter_init(void)
rtas_filters[i].token = rtas_token(rtas_filters[i].name);
}
#else
static bool block_rtas_call(int token, int nargs,
struct rtas_args *args)
{
return false;
}
static void __init rtas_syscall_filter_init(void)
{
}
#endif /* CONFIG_PPC_RTAS_FILTER */
/* We assume to be passed big endian arguments */
SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
{